PROJECT SUMMARY/ABSTRACT People with serious mental illness, about 6% of the US population, have one of the greatest health disparities of any group, with a life expectancy up to 25 years less than the general population. Preventable, obesity- related health conditions due to sedentary lifestyles, poor nutrition, and medications are major causes of this disparity. Despite a variety of evidence-based health promotion practices, we do not know how to effectively transform community mental health organizations to embrace wellness as central to their mission and services. Despite widespread use of Learning Collaboratives and their potential benefits in applying collective problem solving, inclusion of consumer perspective, and quality improvement methods in implementation of evidence- based practices, there have been few (if any) randomized trials evaluating their effectiveness using quantitative outcomes. To our knowledge, the proposed study is among the first to empirically evaluate the effectiveness of a virtual national learning collaborative in implementing a new evidence-based practice. Using an implementation research framework, we propose a cluster-randomized trial of 48 mental health provider organizations to evaluate the effectiveness of two different strategies in the initial implementation of the In SHAPE model of integrated health promotion in mental health organizations. We will test the following study hypotheses: Instruction + Learning Collaborative (I+LC) compared to Instruction Alone (IA) will be associated with: (H1) greater Program Participation (the Primary Service Outcome Study Hypothesis-as measured by the proportion of enrolled individuals who have received an adequate exposure to the intervention defined by attending at least 50% of Health Mentor sessions over 6 months); and (H2) greater Organizational Change supporting health promotion (the Secondary Implementation Outcome Study Hypothesis-as measured by the General Organizational Index adapted for In SHAPE). In addition, we will examine exploratory hypotheses that I+LC vs. IA will be associated with: (E1) more rapid Full Program Operation; (E2) greater Program Uptake and Expansion; (E3) greater Program Fidelity; (E4) greater likelihood of Program Sustainability; and (E5) better Participant Outcomes (physical activity; nutrition and weight loss). Finally, we will document the incremental time and costs associated with the virtual Learning Collaborative, and (E6) explore the effect of Organizational Change supporting health promotion on Program Participation, and of Learning Collaborative Adherence on Program Participation. This study addresses a major gap in the implementation research literature on the effectiveness of Learning Collaboratives compared to usual implementation, including use of virtual (interactive video) as a practical and scalable implementation strategy. Findings from this study may also help inform how to overcome the challenge of implementing a new evidence-based practice demanding organizational transformation among resource-limited providers when the new practice necessitates a shift in mission, scope of practice, type of services delivered, and new financing.